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Plug & Charge - A Deep Dive

1.6K views 36 replies 8 participants last post by  Arob  
#1 ·
By now, most of us have heard the term Plug & Charge. What is it, and how beneficial is this technology, is it safe and secure? Is it the best solution? Let's dig in.

History

Ya, I know, this wasn't your favorite subject in school. But knowing a bit of history can help frame a subject, so here we go.

While we are still in the early days of EVs, we have already come a long way. We still have remnants of the original billing methods used for public charging, namely an app linked to your credit or debit card, and used only on public chargers operated by that particular company. While this is effective, it starts becoming complex when there are many networks, each with their own app, each requiring you to enter your credit or debit card info into the app, and maintain it every time you get a new card.

Further, each of these apps have maps to help you find their chargers, but not necessarily all chargers where you are headed. And once you do find a charger, each network tends to have slightly different processes you need to use to activate a charging session.

In short, the emerging problem is one of too many variables that make matters confusing to people who are already struggling to grasp the newness of the paradigm shift of driving EVs after a lifetime of driving ICE vehicles. So, how do we simplify things? That is where ISO15118 Plug & Charge (P&C) comes in.

In 2012, Tesla began installing their own network of chargers, using proprietary communication protocols, for exclusive use by those who purchased a Tesla. Tesla had the foresight to grasp a concept hidden deep in the draft CCS specifications, using a vehicle's unique identifier (VIN) passed during the handshake of a fast charging session to link the car to an account in their billing system. This idea was implemented in Tesla's early days, and was simply referred to as Plug & Charge because of the actions a driver went through to start charging, namely to plug in and charging would automatically start.

What Tesla "invented" was something a few other networks eventually implemented, and is generally referred to as AutoCharge. While it looks and feels like Plug & Charge in that the driver simply plugs in and magic happens, it still faces the challenges of maintaining accounts on each of the networks. Further, it lacked security, ie the VIN is sent over the connection between EV and EVSE in plain text. So, it was a partial solution, only addressing the activities at the "pump", but not solving the multiple account problem. For Tesla, this wasn't a problem, they had successfully convinced their customers that there was no need to go elsewhere for charging, just use the Tesla network, and you can go anywhere.

From the early days of CCS charging working groups, the IEEE sought to take on this problem in a more comprehensive way, one that would eliminate all the accounts, only requiring one account to charge everywhere. This work began in the early 2010's, and the specifications have been revised a few times, but the resulting ISO15118-20 Plug & Charge specification (adopted in 2018 I believe) is finally in an (almost) workable state.

What is the High Level Concept of Plug & Charge?

Conceptually, the idea is for drivers to be able to maintain a single account to pay for charging on every network. Simple concept, but a bit complex to do this in a secure manner. Here is a visual of the relationships between driver and networks:
Image

Notice how the Automaker becomes a proxy for the driver in the P&C scheme. In business terminology, the Automaker becomes the party who is responsible for paying the network for charging fees, also commonly referred to as the "Billing Entity".

While only a few networks currently support ISO 15118 P&C, the goal is to eventually get all networks to get in on the solution. Throughout this article, I will focus on the end state, but know this may take several years to become reality.

How is this Accomplished Securely?

This gets a bit complicated, but hang in there, I will try to simplify it. In the computer world, e-commerce sites, banks, etc adopted the idea of using encrypted internet sessions for financial transaction. To accomplish this, they developed the use of certificates containing Public and Private Keys used in mathematical algorithms to generate dynamic encryption keys.

A Public Key Infrastructure (PKI) scheme was the mechanism that would enable unique encrypted keys, to be used in every secure session over public networks (the Internet). PKI methods are well understood by the professionals who maintain the system, but it is generally a pretty fuzzy concept for consumers. Suffice it to say, the methodology is as secure as anything humans have devised to date, I won't spend too much time digging into the details, but to those who are so inclined, there are many great resources available on the Internet that can help you learn more on the subject. For me, it took several years of using this technology to really gel in my mind, and I was responsible for an end to end infrastructure in a relatively small computer lab environment.

When the IEEE was searching for ways to securely manage a billing schema for P&C, they borrowed the concepts used in secure Internet solutions rather than create something on their own. This has a few benefits, not least of which is a full body of understanding and documentation to help Charge Point Operators (CPOs) and Automakers who would be setting up secure methods of handling billing on behalf of their customers.

PKI relies on a hierarchy of Certificate Authorities (CA), the entities that are widely trusted, and are responsible for issuing and maintaining certificates used in the PKI systems. In the computer world, there are many public and private trusted Authorities, and modern Operating Systems install and maintain the Public "Root" certificates in the computer's "Trust Store" on behalf of end users.

A variation of the public PKI is a Private PKI where a company (say your employer) issues certificates. This requires some additional work to insert the employers root certificate into the computer's trust store, and if used widely, becomes complicated to maintain. Most of the complication simply because once it is setup, you tend to forget about it, but certificates have start and end dates, so if they expire...you get it.

When the IEEE defined the PKI schema for Vehicle to Grid and Plug & Charge (they both use the same certificate hierarchy), they struggled with defining a top level certificate authority (CA) for the entire schema. Initially, a German charge point operating (CPO) company, Hubject was to assume this role, but competing CPOs, and players in other regions (Asia, North America, etc) were hesitant to accept this CA.

In the grand scheme of PKI stands the concept of a Top Level CA, and intermediary or so called subordinate CAs. The ultimate solution, easy for those responsible for maintaining things is a single trusted Top Level CA (aka the Top Level Root CA). Until mid-2024, no such Root CA had been agreed to for North America, though EU and perhaps other regions were using the original Hubject Root CA.

Several years ago, EA started offering ISO15118 P&C to a select number of automakers (Ford, VW Group, and a few others). As there was no agreement on an acceptable Root CA, Electrify America inserted itself as the root authority, much like your employer might do in a private PKI schema mentioned above. While this worked, it meant that the next network that wanted to adopt P&C would need to create their own private PKI, and automakers would need to say on top of them all.

Where Does it Stand Now?

In North America, the parties involve in the NEVI initiative of federally subsidized public chargers got together and came to an agreement on a Top Level Root CA. I don't know who this is, and it doesn't really matter for this discussion anyway. So, there is now a public framework to proceed to a universal system of ISO15118 P&C.

Currently, I am only aware of 3 networks embracing the Public version of the PKI schema, these are Tesla, Ionna, and Mercedes (partnering with Chargepoint). As mentioned above, EA also offers P&C, but using a Private Root CA schema, which is likely to convert to a Public Root CA at some point in the future.

Given recent political changes, NEVI is likely to wind down its role as a Government force to coordinate expansion of public charging. But the promise of a simpler method still exists, and I expect other networks will eventually get on board.

Does ISO15118-20 P&C Solve All of the Problems?

No, not really. Sorry!

While ISO15118 P&C solves the multiple account problems, not all networks participate (yet). Further, because the nature of having the Automakers coordinating the transactions, there is anonymity for the driver, which may sound great, but also has a drawback.

Some CPOs offer premium membership plans, pay a monthly fee and get discounted charging rates for the month. These include Electrify America (EA) Pass+, Tesla, and EVgo. To enjoy the benefits of these plans, the CPO needs to know it is you that is authorizing charging. So, the anonymity of P&C obscures this, they don't know it is you, they just know your automaker (Hyundai) is authorizing payment on behalf of someone. This also holds true for those who want to use ChargePoint credits at Ionna.

Can the premium plan problem be solved? Sure, but it probably isn't currently a priority. As mentioned before, VIN is passed to the EVSE during the handshake with the charger. But that isn't a secure transaction. Ultimately, it may take some additional coordination between OEMs and CPOs to come up with a method of premium discounted services within the P&C schema. If I were to guess, Ionna will lead the way on this. Why? Because of the relationship between the OEMs investing in Ionna, and the CPO itself. Tesla could also be an influencer in a solution to this problem.

Deep within the details of PKI is another piece of data that could be used to determine premium account status. Bear with me, this one is a bit in the weeds...

Each Leaf Certificate (the certificate Auto makers issue to your car) contains a unique serial number. This, along with the serial numbers of the issuing authorities (the Root and Subordinate CAs) are the basis for how certificates are validated. If your certificate serial number were somehow linked to your account with the network, it would be possible to extend discounted pricing...but that is probably way too complicated due to the transient nature of certificates (they expire, are revoked if you don't pay your bills, or are canceled if you sell the car). It would be overly complicated for CPOs to stay on top of it.

The more likely method might be a premium membership with your Automaker. This, coupled with some sort of revenue sharing with CPOs of the membership fee for the premium service might enable a discounted method. We don't need to dig into the how's for this, suffice it to say it is conceptually possible, but not currently a priority. That might be a future enhancement, and might even come in the form of an IEEE revision to the ISO15118 P&C specifications.
 
#2 ·
The more likely method might be a premium membership with your Automaker.
I think this would be the hot setup for the consumer. I'd expect the premium to be a bit higher since it would cover all the CPOs in the system and the auto maker and those CPOs would want to share the financial hit, but it would be worth it on a long trip compared to paying for multiple discount plans with multiple CPOs and then not getting to use P&C on the trip after all.
 
#7 ·
My thinking is a bit broader WRT this. Perhaps those networks that offer premium pricing would get a % of revenue automakers collect for premium, based on some historic use patterns. For example, Hyundai would pay 25% of subscription fees collected to Tesla if 25% of Hyundai's customers use Tesla chargers (vs EA, Ionna, etc). In turn, Hyundai would advertise the benefit of their premium membership offering as providing discounted rates on the participating networks. It might even encourage more networks to offer premium pricing.

They could even price it as an annual subscription to reduce churn. In other words, if most people subscribe for 2 months per year under current plans, make the annual subscription cost something close to the annualized cost of two or three months of subscriptions, plus a little for running the game. Bundling it with other Bluelink services might even increase the take rate more, like discounted parking via Hyundai Pay.

I think the point is, getting the service launched in the first place is enough of a task, enhancing it later is an incremental effort.
 
#3 ·
In North America, the parties involve in the NEVI initiative of federally subsidized public chargers got together and came to an agreement on a Top Level Root CA. I don't know who this is, and it doesn't really matter for this discussion anyway. So, there is now a public framework to proceed to a universal system of ISO15118 P&C.
I believe SAE is serving as the Root CA for North America, as announced last December.
 
#5 ·
As someone that works in cybersecurity, I'd argue that the who does matter, but it's not something the average user needs to worry about. You want someone with a trusted reputation and a culture of well defined processes and standards. I'd argue that SAE meets these criteria, so there's not much to worry about. I think most people will just treat the process as magic, and not need to know the details. For those that do want to dive in to the details, the root CA provider is worth knowing.
 
#11 ·
I meant to include a short discussion of alternatives, the obvious one being Credit Card terminals.

My experience with CC readers at public chargers isn't good. I find a high failure rate, not sure why, perhaps it is a rarely used option so networks pay less attention to it. Or maybe it is the remote locations for many chargers being more difficult to handle CC transactions?

The other part of the Credit Card piece is transaction fees. This amounts to a large % of a total transaction cost as the fees are generally a flat fee, plus a % of the transaction amount. By offloading the collection part to the automakers by adopting P&C, the networks cut their costs considerably.

The way Hyundai is handling this seems to be charging your credit card for each transaction, but they could find consolidating these into daily, or weekly charges to your CC could reduce their costs considerably (fewer flat transaction fees). The cost of delaying processing a CC charge by a day, or week could be offset by a premium billing fee tied to the discounts on networks. So, if you sign up for a premium billing plan, you are billed weekly and get discounts at the participating networks. It could further justify charging a bit more for the service.
 
#15 ·
Interesting writeup, thank you.
Over here in Norway, the ev owners association (Elbil foreningen) have a blue rfid tag members can use, that works on a lot of charging networks across Europe, somewhere above 750000 charging points last i read, so probably gone up a bit more 😁

You set up your chosen payment option in your account with them (credit or debet card) and they are then your roaming operator, and handles billing etc.
They also have premium membership options for ionity.
I keep that tag as a backup in my car. Same as the charge my hyundai card.
I primary use an rfid card that I have linked to about a dozen different providers, including a roaming operator/provider, just to mess stuff up a bit 🤣
Car is also set up with autocharge for a couple of them.
 
#17 ·
Interesting writeup, thank you.
Over here in Norway, the ev owners association (Elbil foreningen) have a blue rfid tag members can use, that works on a lot of charging networks across Europe, somewhere above 750000 charging points last i read, so probably gone up a bit more 😁

You set up your chosen payment option in your account with them (credit or debet card) and they are then your roaming operator, and handles billing etc.
They also have premium membership options for ionity.
I keep that tag as a backup in my car. Same as the charge my hyundai card.
I primary use an rfid card that I have linked to about a dozen different providers, including a roaming operator/provider, just to mess stuff up a bit 🤣
Car is also set up with autocharge for a couple of them.
Right, we have some roaming agreements in the states too. Hyundai provides a $400 ChargePoint credit with new 2025 model purchases, and Chargepoint has roaming agreements with EVgo, EVConnect, Ionna (the US equivalent of Ionity). They also offer RFID cars which work on many if not all of these other networks.

Autocharge, while more convenient than messing with RFID and apps is still tied to individual networks. So, to use Autocharge on EVgo, you have to have an EVgo account, add your car to their billing system (VIN), activate the first time using the app to complete the enrollment, then it works on subsequent sessions on the EVgo network, but no others.

ISO15118 P&C attempts to answer the multiple accounts problem, but it will take years for everyone to get on board. 2025 models are the first to get this capability, thus the article to help people understand what it is all about. Hyundai has been offering ISO15118 P&C in EU, I think with Ionity for some time, so not so new there.

Thanks for adding your regional info, it helps (me at least) to understand a bit about how things work elsewhere.
 
#21 ·
Plug and charge is overrated. With these new chargers it doesn't take that long at all for the car to engage with the charger or the payment process. Plug and charge is a Tesla thing so leave it as a Tesla thing. Everybody's now adapting to the nacs connector and you see how well that's going. The last time I went to DC fast charger I activated the crger with my charge point app. It took about 30 to 40 seconds for it to engage the car and start the payment process. I don't know what I could do differently with 30 or 40 seconds. So that's my thought on plug and charge. Yes it would be a lot more convenient for drivers if everyone had the same app but really it doesn't make a ton of difference. Just remember when you were driving your ice vehicle you still had to activate the pump by going inside or with your credit card. So I don't see why electric vehicles need to be any different.
 
#22 ·
Granted, but the current methods are death by 40 lashes. The problem is, you need apps for nearly every network on long trips to unfamiliar places. Currently, there are 44 networks in the Plugshare filters for N. America, but there are actually probably 50% more that are lumped under the "other" category. So theoretically, we are talking about so many apps, each with your CC info on file. Given the rate of security breaches these days, each one of these is a security exposure. Maintaining them all, nothing less than a nightmare.

Sure, that is extreme, none of us routinely travel outside of a relatively small circle, and many cross continent routes are served by a handful of networks well enough to skip many of the bit player networks.

Recently, we went through 4 new CC from our bank, we kept seeing fraudulent activity and each time, I had to update CC info in a dozen charging apps. Some charge $1 then credit back to validate the card, and in the course, I had the card freeze due to suspected fraudulent activity because of all the validation hits. So the next time, I spread the updates over the course of several days, 2 at a time. If that had happened on the road, what a nightmare with limited network coverage.

In the large multinational corporation I worked for, I held a position which was sort of an enforcer for sales process used globally for thousands of products, hundreds of product managers. Each product team routinely came up with great ideas and asked us to allow them to use them. More often than not, we said no, because sales people get too confused with too many different processes and tools. In other words, we were responsible for containing shelter skelter!

The public charging industry has no such standards controls, sure the communications protocols are standard, but the way you activate charging varies, sometimes only slightly, but collectively, all the little differences add unnecessary confusion, particularly for new owners, or new networks.

So, P&C attempts to address the multi app, multi account, and varying process problems. In its current state, it hasn't achieved that yet, P&C isnt widely supported...but you have to start somewhere.

As stated above, there are still some kinks to be ironed out. In my mind, the discounted charging part is one of the biggest remaining challenges, and it going to take some innovative thinking and broad coordination. And again, for the automakers and networks, the more standard those improvements are, the quicker companies will embrace them.

So, in its current form, it isn't such a game changer, particularly for people who are able to use only a handful of networks in the circles they travel in. But, it has the potential to create an incredibly simple solution if the players can work through the remaining pain points, and they will, eventually.
 
#28 ·
Tap and pay using your phone's built in wallet app is pretty secure. With credit cards, it can be, though it depends on whether the bank that issued the card did it right. There was a research attack 20 years ago that found many cards exposed names and card numbers in the clear. The banks claimed those were aberrations, and that "most" cards were encrypted to prevent that. It's likely the tech has gotten more secure in the intervening years, but I don't work in the banking industry, so can't say if their policies have kept up. When they were moving away from primary reliance on magnetic stripes, the US banks opted for the less secure, and less convenient, chip and signature method, rather than the chip and PIN that more of the rest of the world adopted. The reason for this was because signature verification was more complex, they could charge more per transaction. I'll leave it to the imagination of the reader to guess how much of this extra processing cost was actually devoted to enhanced signature verification methods.
One potential problem with using tap to pay for charging is that most countries limit them to low value transactions without additional verification. In much of Europe, for example, the limit might be €25 or €50 before the user is prompted to enter their PIN. This needs a working PIN pad, which is another thing that can go wrong. This won't impact RAN chargers in the US, since most cards aren't PIN enabled, so don't have that security check.